1. Technical Field
The present invention relates to an ultrasonic measurement apparatus, an ultrasonic diagnostic apparatus, an ultrasonic measurement method, and the like.
2. Related Art
In ultrasonic measurement apparatuses (ultrasonic diagnostic apparatuses), synthetic aperture processing in which focusing can be formed in overall region of an observation region is adopted thereto in order to obtain favorable resolution throughout a wide region in an ultrasonic image. According to the aforementioned technique, focusing can be formed with the fewer number of times of transmissions and receptions, and processing is performed so as to be able to attain a high frame rate and high resolution.
Among methods of the synthetic aperture processing, there is known technique in which plane waves are used as transmission waves. For example, JP-A-2003-220059 discloses technique of performing the synthetic aperture processing in consideration of diffraction characteristics of ultrasonic waves while using the plane waves as transmission waves. Gabriel Montaldo, “Coherent Plane-Wave Compounding for Very High Frame Rate Ultrasonography and Transient Elastography”, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 56, no. 3, 2009. (hereinafter, referred to as Non Patent Literature 1) discloses technique of acquiring resolution equivalent to that in multistage-focus processing which is known as technique in the related art being different from the synthetic aperture processing, and realizing a high frame rate. Specifically, according to Non Patent Literature 1, the synthetic aperture processing is performed by transmitting plane waves which do not allow focusing of a beam, thereby realizing resolution equivalent to that in the multistage-focus processing in the related art with the fewer number of times of transmissions.
As disclosed in Non Patent Literature 1, it is possible to acquire an ultrasonic image having equivalent resolution compared to that of technique in which the plane waves are not used, with the fewer number of times of transmissions by using plane waves as transmission waves. However, when transmitting a plane wave from an element array (an ultrasonic transducer element array), the plane wave is transmitted to a predetermined region, but a wave other than the plane wave (for example, a spherical wave) is transmitted to other regions.
According to the technique disclosed in Non Patent Literature 1, it is not possible to capture a signal of a wave other than the plane wave. Therefore, an aperture width effective for transmission becomes small in the technique, thereby leading to a disadvantage in that resolution of an obtained image is degraded as a result thereof.